1. Field of the Invention
The present invention relates to magnetic disk apparatus with high-density magnetic information recording performances and control methodology thereof.
2. Description of the Related Art
Conventionally known magnetic disk apparatus adaptable for use as external storage devices or else of computers are typically designed to include a rotation mechanism for driving more than one magnetic disk to rotate or spin at high speeds, and a magnetic head slider with a built-in recording/reproduction element. The magnetic head slider is supported by a load beam so that it is position-determined and placed along the diameter of the magnetic disk. The magnetic disk apparatus is arranged to record magnetic information at a desired track(s) on the magnetic disk and also reproduce such stored magnetic information out of the magnetic disk while letting the magnetic head slider relatively move over the magnetic disk. The magnetic head slider is designed to use an air lubrication shaft bearing for flotation by wedge film effects of the air. The use of such structure precludes any direct physical contact between the magnetic disk and magnetic head slider.
In addition, typically employable methodology for achieving higher recording densities and larger storage capacities of magnetic disk apparatus with or without reducing the size and shape thereof includes methods of increasing track densities and methods of increasing on-track linear recording densities. The on-track linear record density increasing methods may in turn include, but not limited to, a method for increasing the sensitivity of a recording/reproduction element used, and a method of reducing the distance between the record/reproduction element and its associative record carrier body, also known as recording medium. One typical approach to effectively achieving the latter method is to reduce the distance between a magnetic head slider and magnetic disk, that is, the flying height of such slider.
On the other hand, traditionally in cases where the flotation amount of the magnetic head slider is designed, there are provided certain margins which are determined by taking into account of any possible flotation amount reduction occurring due to machining variation of the magnetic head slider and/or environmental differences such as atmospheric pressure differences. If such margins are removed away, then it is possible to further shrink the resultant flotation amount of the record/reproduction element.
A converter for use in recording devices capable of individually precise or micro-adjusting the distance between a recording/reproduction element and a magnetic disk has been disclosed in JP-A-62-250570. The converter as taught thereby is arranged so that a built-in miniaturized or micro actuator is mounted at part of the magnetic head slider, which actuator is generally formed of more than one piezoelectric element. Assembling such piezoelectric micro-actuator enables accomplishment of individual micro-adjustability of the distance between the record/reproduction element and the magnetic disk.
The scheme for controlling the flotation amount of such record/reproduction element using the microactuator as recited in the above-identified Japanese document is generally called the active head slider scheme. This document also suggests therein another method for using the actuator piezoelectric element also as a sensor for detection of contact between the record/reproduction element and magnetic disk.
Another prior art method is available for designing a magnetic resistive element making up a magnetic information reproduction element in such a way that it also do double-duty as a contact detection sensor, as has been recited in JP-A-10-233070. This method makes use of a technique for detecting a change in resistivity occurring due to a temperature variation upon contacting, also known as thermal asperity, in a way independent of standard or ordinary magnetic information read/write sessions.
On the other hand, in order to meet the need for achievement of higher recording densities of information, it should be required to further reduce the distance between the record/reproduction element and the magnetic disk. This in turn strictly requires that design be made within a specific flotation amount region in which intermittent physical contact takes place due to micro-unevenness configuration on the magnetic disk side and also on the magnetic head slider side.
Additionally, from a view point of preclusion of the magnetic head slider""s unwanted vibration due to physical contact and prevention of thermal asperity, a need is felt to minimize the frequency of physical contact events and the volume of an impingement or collision portion. Due to this, it is required that the magnetic head slider be designed to have its flotation amount that is set at a carefully selected level or greater. Accordingly, the wideness of an allowable region that is limited by upper and lower limit values of the flotation amount is presently made further narrower than was used conventionally.
Unfortunately, with the active head slider scheme as taught from the above-identified former Japanese citation JP-A-62-250570, it is required in order to attain the required high record density to further shrink the distance between the record/reproduction element and the magnetic disk, although the scheme offers enhanced effectivities for reduction of the distance between the record/reproduction element and magnetic disk.
As per the method for detecting a resistance change occurring due to a temperature variation upon contacting, i.e. thermal asperity, independently of ordinary magnetic data read/write operations as suggested by the latter document JP-A-10-233070, this method is encountered with a risk of frequent occurrence of intermittent physical contact due to microconfiguration on the magnetic disk side and on the magnetic head slider side, causing a serious problem as to likewise decreases in durability and reliability.
The present invention is made to avoid the problems described above, and its primary object is to provide a new and improved magnetic disk apparatus capable of significantly reducing the length of a time period for physical contact between a recording/reproduction element and its associative magnetic disk along with a control method thereof, thereby improving the durability and reliability of the magnetic disk apparatus.
To attain the foregoing object, the instant invention provides a new and improved magnetic disk apparatus which includes a rotation mechanism that is provided within an apparatus main body for driving more than one magnetic disk to rotate, a magnetic head slider as movably provided in a radial direction of the magnetic disk for being floated by an air shaft bearing in adjacent to a surface of the magnetic disk with a specified distance therefrom, a recording/reproduction element provided at a distal end of the magnetic head slider for recording and reproducing magnetic information on and from the magnetic disk, a drive unit for changing a distance between the record/reproduction element and the magnetic disk, and a position determination unit which supports the magnetic head slider and is operable to perform position determination of the magnetic head slider in the radial direction of the magnetic disk, wherein the apparatus is specifically arranged to further include a detection unit for causing, upon receipt of a command for recording or reproduction magnetic information to or from the magnetic disk, the drive unit to gradually reduce a distance between the record/reproduction element and the magnetic disk and for detecting contact between the record/reproduction element and the magnetic disk, and a control unit for controlling the drive unit in such a way that when the detection unit detects contact between the record/reproduction element and the magnetic disk the record/reproduction element shifts in position by a fixed amount thereby letting the distance increase accordingly.
With such an arrangement, it is possible to achieve a low flotation amount corresponding to the required high recording density irrespective of machining variations of the individual magnetic head slider and in-use environments including, but not limited to atmospheric pressure differences, while at the same time making it possible to prevent any possible continuous physical contact between the record/reproduction element and magnetic disk, resulting in preclusion of contact vibration and/or thermal asperity. This in turn enables improvement in linear recording density and thus further increases in storage capacities of the magnetic disk apparatus while further miniaturizing the magnetic disk apparatus.
In addition, the record/reproduction element is specifically arranged so that this element is kept lower in its flotation amount only within a shortened time period for reading/writing data to/from the magnetic disk and, within the remaining, long time periods, is held in a high flotation amount state which is almost free from risks of such physical contact. Accordingly, it is possible to prevent occurrence of damages of the record/reproduction element and magnetic disk otherwise occurring due to physical contact therebetween. This in turn makes it possible to significantly improve the durability and reliability of the magnetic disk apparatus.
The magnetic disk apparatus of this invention is the one that is arranged so that the magnetic head slider is generally structured from a primary slider and a secondary slider, wherein the drive unit is provided along the primary slider and the secondary slider while letting the record/reproduction element be provided at a distal end of the secondary slider.
With such an arrangement, the responsibility during shifting of the recording/reproduction element may be improved while simultaneously facilitating execution of subtle shift operations with increased accuracy.
The magnetic disk apparatus of the invention is such that a ramp for permitting escape of the magnetic head slider is provided outside of an outer periphery of the magnetic disk to thereby let the magnetic head slider escape to the ramp before interruption of the apparatus main body or alternatively when a read/write command is absent within a prespecified length of time period while causing the record/reproduction element to shift so that the distance between the record/reproduction element and the magnetic disk increases before recovery of the magnetic head slider from the ramp to a location over the magnetic disk and also before the magnetic head slider escapes from a location over the magnetic disk to the ramp.
With such an arrangement, the magnetic head slider is driven to move from over the magnetic disk and escape to the ramp before interruption of the apparatus main body or alternatively within a predetermined length of time period in which any read/write commands are absent while permitting the record/reproduction element to be shifted in position so that the distance between the record/reproduction element and the magnetic disk increases accordingly prior to the escape of the magnetic head slider from over the magnetic disk to the ramp. Thus it becomes possible to preclude damages otherwise occurring due to physical contact between the record/reproduction element and magnetic disk in loading and unloading events.
The magnetic disk apparatus of the invention is also such that in case the drive unit is arranged to function also as an acceleration detection unit, when the acceleration detection unit detects zero gravity or alternatively upon detection of rapid acceleration, it causes the record/reproduction element to shift in position thus letting the distance between the record/reproduction element and the magnetic disk to likewise increase at high speeds.
The use of such an arrangement permits, when the acceleration detection unit detects zero gravity or alternatively detects any rapid acceleration, quick removal of a positional change or displacement of the drive unit causing the record/reproduction element to shift into its high flotation state or adversely displacing the drive unit toward the high flotation state side thus letting the record/reproduction element shift into the high flotation state thereof. Thus it is possible, even upon occurrence of erroneous or accidental fall-down of the magnetic disk apparatus, to sufficiently retain the required flotation amount of the record/reproduction element. This in turn makes it possible to successfully prevent damages of the magnetic head slider and/or magnetic disk otherwise occurring due to application of shocks when falling down.
A method of controlling magnetic disk apparatus in accordance with the invention is a control method of magnetic disk apparatus which includes a rotation mechanism provided within an apparatus main body for driving more than one magnetic disk to rotate, a magnetic head slider movably provided in a radial direction of the magnetic disk for being floated by an air bearing in adjacent to a surface of the magnetic disk with a specified distance therefrom, a record/reproduction element provided at a distal end of the magnetic head slider for recording and reproducing magnetic information on and from the magnetic disk, a drive unit for changing a distance between the record/reproduction element and the magnetic disk, and a position determination unit for supporting the magnetic head slider and for performing position determination of the magnetic head slider in the radial direction of the magnetic disk, wherein the method includes the steps of: causing, upon receipt of a command for recording or reproduction magnetic information to or from the magnetic disk, the drive means to gradually reduce a distance between the record/reproduction element and the magnetic disk; and, upon detection of contact between the record/reproduction element and the magnetic disk, performing proper shift amount estimation processing for shifting the record/reproduction element by a fixed amount thereby letting the distance increase accordingly.
With the use of the method above, it is possible to achieve a low flotation amount corresponding to the required high recording density irrespective of machining variations of the individual magnetic head slider and in-use environments including, but not limited to atmospheric pressure differences while at the same time making it possible to prevent any possible continuous physical contact between the magnetic head slider and magnetic disk, resulting in preclusion of contact vibration and/or thermal asperity. This in turn enables improvement in linear recording density and thus further increases in storage capacities of the magnetic disk apparatus while further miniaturizing or downsizing the magnetic disk apparatus.
The method of controlling the magnetic disk apparatus of the invention is the one wherein the proper shift amount estimation processing is performed at least one time after completion of assembly of the apparatus main body or alternatively done at least one time per start-up of the apparatus main body or still alternatively done at least one time per a prespecified time interval during startup of the apparatus main body while simultaneously letting a resultant proper shift amount be stored in a memory for use in letting the record/reproduction element shift by the proper shift amount in ordinary read/write events.
With use of the method, it is possible to shorten a response time with respect to a read/write command, which in turn makes it possible to lessen the frequency of contact between the record/reproduction element and magnetic disk while at the same time significantly reducing the length of a read/write time duration. This enables reduction of wear otherwise occurring due to physical contact between the record/reproduction element and magnetic disk.
The magnetic disk apparatus control method of the invention is the one wherein the proper shift amount estimation processing is done when the magnetic head slider is at an outer periphery of the magnetic disk and also done when it is at inner periphery thereof respectively for one time for storing resultant proper shift amounts at the outer periphery and the inner periphery in memories respectively while in the ordinary read/write events performing linear interpolation of the proper shift amounts at the outer periphery and the inner periphery in accordance with a position in a radial direction along the diameter whereat the magnetic head slider presently resides to thereby calculate a proper shift amount at the position thus permitting the record/reproduction element to shift accordingly.
Using the method makes it possible to accurately calculate an adequate or proper shift amount of the magnetic head slider at any given positions along the diameter of such magnetic disk while significantly shortening both a time as required for the proper shift amount estimation processing and a time period of contact between the record/reproduction element and the magnetic disk due to the same processing.
The magnetic disk apparatus control method of the invention is the one in which the proper shift amount estimation processing is done a plurality of times when the magnetic head slider is at respective different radial positions of the magnetic disk thereby storing a combination of resultant proper shift amounts and a plurality of radial positions in a memory while in the ordinary read/write events performing linear interpolation of proper drive amounts of two points as selected from the combination adjacent to the above-identified position or alternatively interpolation of more than three points by a polynomial to thereby calculate a proper shift amount at the position thus letting the record/reproduction element shift accordingly.
Using the method makes it possible to accurately calculate the proper shift amount of the magnetic head slider at any given radial position along the diameter of the magnetic disk while simultaneously enabling significant reduction of both a time as taken to perform estimation processing of such proper shift amount(s) and a contact time duration for contact between the record/reproduction element and the magnetic disk due to the same processing.
The magnetic disk apparatus control method in accordance with the invention is the one that performs the proper shift amount estimation processing for at least one time when a magnetic information reproduction signal becomes weaker in intensity.
With the method, in case where contaminants are deposited on the record/reproduction element during long-term operation resulting in a decrease in intensity of the magnetic disk""s magnetic information playback signal, the proper shift amount estimation processing is done thereby making it possible to remove away such contamination at the record/reproduction element section, which in turn enables achievement of long-term operabilities of the magnetic disk apparatus while reducing or minimizing complexities in maintenance thereof.